1. Field of the Invention
This invention relates, generally, to solid-state load protection systems and more particularly to a field testing feature enabling the user to test the operation of an overcurrent trip function and the associated circuitry.
2. Description of the Prior Art
It is known that some load protection systems have various protection functions such as current overload, phase loss, and ground fault sensing. These functions generally provide a trip time for a circuit breaker and associated load which is inversely related to the square of the current flowing in the load to be protected. Therefore, an inverse time relationship is generally utilized whereby the time between a fault which is sensed and trip out are inversely related such that a high overcurrent will result in a very short period of time for device trip out and a relatively low overcurrent fault will result in a substantially longer time before trip out. Types of devices which accomplish the above can be found in U.S. Pat. No. 4,021,703, "Phase Imbalance Detection Circuit", issued May 3, 1977 to Gary, et al; U.S. Pat. No. 3,996,499, "Zener Diode Effect on Long Acceleration Module", issued Dec. 7, 1976 to Gary, et al.; U.S. Pat. No. 3,818,275, "Circuit Interrupter Including Improved Trip Circuit Using Current Transformers", issued June 18, 1974 to Shimp and U.S. Pat. No. 3,602,783, "Circuit Breaker Device Including Improved Overcurrent Protective Device", issued August 31, 1971 to Engle, et al. all assigned to the assignee of the present invention. However, the above-mentioned patents only allow a user to know that the solid-state load protection system is functioning properly during an actual overload condition or with the aid of external test equipment.
It is desirable to have a load protection system whereby the user may test the operation of the overcurrent trip function without the use of test equipment or creating an actual overload condition. It is also desirable to have a test feature which enables the user to check the reset function of the load protection system.